The digestive and metabolic utilization of the dietary protein: effect of clenbuterol and protein level

The influence of a beta-agonist, clenbuterol, added to the diet at 0, 30 and 50 mg/Kg was studied on the digestive and metabolic use of the dietary protein in Wistar rats of two different weights (70 and 200 g). The rats had been fed diets containing different protein levels (4, 10 and 15%). Treatment with clenbuterol did not have any effects on the absorption of the dietary protein in any of the studies released. The beta-agonist did not alter fecal nitrogen excretion nor did it change the digestion coefficient of the protein at the doses used. Clenbuterol significantly increased (P less than 0.01) urinary nitrogen excretion in younger animals fed diets containing low levels of protein (4%). On the other hand, in animals of greater age/weight that had been fed diets with a sufficient protein content (15%), the beta-agonist significantly reduced urinary nitrogen excretion (P less than 0.001). From the results of this study, it can be concluded that in order that clenbuterol can significantly increase nitrogen balance and protein retention, the animals must be given a sufficient exogenous protein intake and they must not be at a stage of maximum growth potential.